Process for preparing 2, 6-dimethylmorpholinylmercaptobenzothiazole



United States Patent ()flice 3,071,585 Patented Jan. 1, 1963 3,071,585PROCESS FGR PREPARING 2,6-D11VIETHYLMOR- PHOLINYLMERCAPTOBENZOTHIAZOLE(Iliarlcs E. Graiiiel, Midland, and Henry Vollk, Bay City,

Mich, assignors to The Dow Chemical Company, Midland, Mich, acorporation of Delaware No Drawing. Original application Dec. 30, 1957,Ser. No. 705,769. Divided and this application Nov. 27, 1959, Ser. No.855,544 1 Claim. (Cl. 260-2471) This invention relates to a newcompound, 2-[4-(2,6- dimethylmorpholinyl)mercapto] benzothiazole,hereinafter referred to as DMMBT, and to process for its production.

Mercaptobenzothiazole, hereinafter referred to as MBT, has beenoxidatively condensed with amines to form sulfenamides. However, whenthese previously known processes are applied to the condensation of2,6-dirnethylmorpholine (hereinafter referred to as DMM) with MBT, thedesired product has been obtained only in low yield and low purity, themajor undesired by-product being benzothiazyl disulfide.

It has now been discovered that DMMBT can be made in high yield andpurity by the condensation of DMM with MBT, provided the reaction isconducted according to the process described hereinafter. It has furtherbeen discovered that DMMBT is a particularly effective delayedactionvulcanization accelerator for use in the curing of natural and syntheticrubbers. Also, it is an effective fungicide and bactericide.

In making DMMBT, four reactants are used: MBT, DMM, caustic alkali andchlorine. While the prior art suggests many variations in procedure forbringing together MBT, amine, caustic and chlorine, it has been foundthat none of them is satisfactory when the amine is DMM.

it has now been discovered that DMMBT can be readily made in high yieldand purity by the simultaneous addition, in substantially equimolecularproportions, of (a) chlorine and (b) an aqueous alkaline solution of MBTcontaining about 1 to 3 moles of alkali metal hydroxide per mole of MBTto an aqueous solution containing about 1 to 3 moles of alkali metalcarbonate and about 1.2 to 3 moles of DMM per mole of MBT to be used,the temperature of the resulting reaction mixture being maintained atabout to 30 C. during the addition. The reaction is quite rapid and iscomplete within a few minutes after the mixing of the reactants iscomplete. The product separates as a solid which may be isolated byfiltration, washed with water and dried to yield DMMBT in high yield andpurity.

The alkali metal hydroxide and carbonate used in the process of theinvention may be those of any alkali metal, particularly those of sodiumor potassium, though in the interest of economy those of sodium arepreferred.

Since the reaction is strongly exothermic, it is necessary to providemeans for cooling the reaction mixture and to mix the reactantsgradually, with effective agitation. Because of this need for gradualmixing of reactants and for adequate cooling and in view of the almostinstantaneous nature of the reaction, the process is especially adaptedfor continuous operation. In such operation, the three reactant streams,(a) chlorine, (b) alkaline MBT, and (c) alkaline DMM, are simultaneouslymetered into a reactor from which is drawn a slurry of the desiredproduct. Substantially complete reaction occurs in the brief time of afew seconds to, at most, a very few minutes.

The following examples illustrate the invention.

Example 1 PREPARATION OF DMMBT Three gram-moles of sodium carbonate and1.3 moles of 2,6-dimethylmorpholine (31% aqueous solution) weredissolved in 800 cc. of water in a vessel equipped with a stirrer andsubmerged gas-inlet tube. While the solution was vigorously stirred,chlorine was bubbled in at the rate of 175 cc. per minute while addingat an equivalent rate a solution of 1.0 mole of MBT and 3.0 moles ofsodium hydroxide in 400 cc. of water. During this mixing operation thetemperature of the mixture was kept at 20-25 C. by external cooling. ThepH of the solution, as measured by a glass electrode, remained at 11-12during the mixing. When all the MBT had been added, the chlorine wasstopped and stirring was continued for 5 minutes. The DMMBT was filteredfrom the resulting slurry, washed with water and dried at 50 C. in avacuum oven to produce a yield of 88% of theory of high grade DMMBT. Itwas a light tan-colored powder containing less than 2% of thecorresponding disulfide.

Example 2 USE OF DMMBT AS A VULCANIZATION ACCELERATOR DMMBT is aneifective delayed-action accelerator for the vulcanization of rubberand, as such, avoids scorching (premature vulcanization) during hotmixing, milling or molding of the rubber, yet facilitates easyvulcanization at slightly higher temperatures. For such use, it isincorporated into the rubber at the rate of about 0.1 to 2% by weight,preferably about 0.5 to 1.0%. Thus, when 0.5% by weight was milled intoa Hevea-HAF compounded tread stock rubber it was found to delayscorching at 250 F., yet permitted ready vulcanization at 280 F. Thefollowing scorch data were obtained by use of the well known Mooneyviscometer at 250 F.

MOONEY SCORCH TEST Minutes Initial 27 10 point rise 38 The samecomposition was vulcanized at 280 F. for 60 minutes, after which it wasfound that excellent vulcanization had occurred.

Example 3 USE OF DMMBT AS A FUNGICIDE When an aqueous spray containing 3lb. of DMMBT per gallons was sprayed on tomato plants which were theninoculated with the test organism, a 55% control of Alternaria solaniwas obtained. The active material may also be mixed with a dust carrierand applied as a dust with good results.

Example 4 USE OF DMMBT AS A BACTERICIDE Nutrient media which readilysupported the growth of the test organisms were modified by theinclusion of 0.5%, by weight, of DMMBT, after which Salmonella typhosa,Staph. aureus, Aspergillus terreus and Rhizopzls nigricans all failed togrow when inoculated on the media.

This application is a division of copending application Serial No.705,769, filed December 30, 1957.

We claim:

A process for making 2-[4-(2,6-dimethylmorpholinyl)mercapto1benzothiazo1e comprising simultaneously mixing (a) about onemole of chlorine, (b) an aqueous solution of one mole ofmercaptobenzothiazole and about 1 to References Cited in the file ofthis patent UNITED STATES PATENTS Tschunkur et a1 June 30, 1936 CarrFeb. 3, 1942 Kinstler Jan. 10, 1956 Sullivan H--. Aug. 14, 1956

